The present invention relates to interface circuitry. More particularly, the present invention relates to interface circuitry for use in vehicle diagnostic equipment.
Originally developed to help automobile engines meet government emissions regulations under the Clean Air Act, On Board Diagnostics using electronic control units (xe2x80x9cECUxe2x80x9d) has increasingly been used to control varied aspects of automobile operations. For example, the ECU is now used to control such functions as anti-lock braking, traction control, anti-theft devices, air bag deployment, and cruise control in addition to controlling engine performance to limit emissions and improve performance.
To control engine performance, the ECU receives signals from sensors such as, and by way of example, air and coolant temperature sensor, mass air flow sensor, vane air flow sensor, exhaust gas recirculation valve position sensor, manifold absolute pressure sensor, oxygen sensor, throttle position sensor, knock sensor and crankshaft position sensor to control valves and switches in the engine. Examples of such valves and switches include the exhaust gas recirculation (xe2x80x9cEGRxe2x80x9d) valve, torque converter clutch solenoid, electronic air control valve, fuel injectors, purge control valve, and positive crankcase ventilation (xe2x80x9cPVCxe2x80x9d) valve.
A useful consequence of the use of ECUs for controlling engine performance is that data representing faulty operation of engine components can be stored in the ECU. This data can then be accessed, in the form of trouble codes, in order to diagnose the engine faults as an aid to repairing the vehicle. Numerous devices have been developed for accessing these trouble codes including, for example, hand held computer programmed scanners. In order to utilize one of these scanners, it must be coupled to the ECU through a diagnostic link connector (xe2x80x9cDLCxe2x80x9d).
Originally each automobile manufacturer utilized different ECUs and diagnostic codes. Steps have been taken to standardize these computer control systems by the issuance of standards by the Society of Automobile Engineers (xe2x80x9cSAExe2x80x9d) for a universal set of diagnostic codes. The SAE has also standardized a sixteen pin DLC, the J1962 connector. As a result, a single xe2x80x9cuniversalxe2x80x9d scanner can now be used for testing all 1996 and later automobiles and, using appropriate adaptors, prior non-standard computer control systems. An example of such a scanner is the hand held GENISYS(trademark) diagnostic scan tool sold by the OTC business unit of SPX Corporation, Owatonna, Mich.
In addition to the diagnostic code reading functions provided by the GENISYS(trademark) scanner, this tool also provides additional functionality as described in co-pending U.S. patent application Ser. Nos. 09/702,751 and 09/468,231, the disclosure of which is incorporated herein by reference. While scanners such as the GENISYS(trademark) tool are a vast improvement over prior devices, improvements can still be made to the circuitry to reduce cost and size.
The foregoing need has been satisfied to a great extent by the present invention wherein in one aspect interface circuitry is provide for an automobile electronic control unit diagnostic scanner. The scanner includes a first resistor, a second resistor and a transistor array. The first resistor is connected at a first end to a collector of a first transistor of the transistor array and at a second end to a first pin of a link connector. The second resistor is connected at a first end to a collector of a second transistor of the transistor array and at a second end to the first pin of the link connector. A plurality of resistance values can be provided at the first pin of the link connector by biasing a base of the first transistor, the second transistor and a base of both transistors.
In another aspect of the invention, the interface circuitry also includes a third resistor connected at a first end to the collector of a third transistor of the transistor array and connected at a second end to the first pin of the link connector. The transistor array is a seven segment display driver NPN array.
In another aspect of the invention a field programmable gate array (FPGA) is electrically connected to the bases of the first, second, and third transistors. First, second, and third inverters are interposed, respectively, between the FPGA and the first, second, and third transistor.
In another aspect of the invention a fourth transistor is provided having a base connected to the FPGA through an inverter. The emitter of the fourth transistor is connected to ground and the collector is connected to a second pin of the link connector through a fourth resistor. A first voltage supply is connected to the emitter of the fourth transistor.
In another aspect of the invention, interface circuitry for an automobile electronic control unit diagnostic scanner is provided including a means for providing a plurality of resistances at a first and second pin of a link connector. Means are also provided for selecting the resistance to be provided at the first and second pin of said link connector. The means for selecting the resistance is a seven segment display driver NPN array.
In yet another aspect of the invention, a method of accessing trouble codes in an automobile electronic control unit is provided. In this method an electronic signal is transmitted from a field programmable gate array. A transistor of a gate array is biased with the transmitted signal and an electronic signal is received at the gate array representative of a trouble code.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.